Log-Ratios Variances

Computes log-ratio (weighted) variances.

Usage

variance(x, ...)

# S4 method for class 'LogRatio'
variance(x, row_weights = NULL, column_weights = TRUE)

Arguments

x

A CompositionMatrix object.

...

Currently not used.

row_weights

A numeric vector of row weights. If NULL (the default), equal weights are used.

column_weights

A logical scalar: should the weights of the log-ratio be used? If FALSE, equally-weighted parts are used. Alternatively, a positive numeric vector of weights can be specified.

Value

A numeric vector of individual variances.

References

Greenacre, M. J. (2019). Compositional Data Analysis in Practice. Boca Raton: CRC Press.

See also

Other statistics: aggregate(), condense(), covariance(), dist, mahalanobis(), margin(), mean(), pip(), quantile(), scale(), variance_total(), variation()

Author

N. Frerebeau

Examples

## Data from Aitchison 1986
data("hongite")

## Coerce to compositional data
coda <- as_composition(hongite)

## Total variance (1)
variance_total(coda)
#> [1] 1.691324

## Metric standard deviation
variance_total(coda, sd = TRUE)
#> [1] 0.6502546

## CLR transformation
clr <- transform_clr(coda)

## Individual log-ratio variances
variance(clr)
#>           A           B           C           D           E 
#> 0.012371857 0.106172753 0.188210073 0.009111225 0.008868299 

## Total log-ratio variance (2)
variance_total(clr)
#> [1] 0.3247342

## Proportionality between (1) and (2)
## See Aitchison 1997
variance_total(coda) * (1 / ncol(coda)) * (1 - (1 / nrow(coda)))
#> [1] 0.3247342